Sensitivity of Concrete's Embodied Carbon Emissions to Cement Direct Carbon Intensity and Material Transportation

Abstract

The objective of this study is to isolate the relative contributions of cement’s global warming potential (GWP) of cement and the impact of transporting concrete materials on the net GWP of a concrete mixture. Environmental product declarations (EPDs) are becoming more commonly used by the cement and concrete industries. EPDs present single point estimates of mid-point indicators, such as GWP, without appropriately indicating the associated uncertainty. However, EPD uncertainty is clearly a concern as established by the General Services Agency (GSA) which published a document suggesting a certain amount of error is associated with the estimated GWP of a concrete product. Infrastructure owner agencies are beginning to collect cement and concrete EPDs and using these to inform benchmark mid-point indicator values for their projects. However, the benchmark values typically provide average information and do not address uncertainty, therefore failing to deliver GSA’s expectations. Therefore, this research explores the sensitivity of GWP to different cement direct carbon intensity values and materials transportation distances using a field dataset of concrete mixture designs from across the country, as well as variations of these parameters for a theoretical mixture design. This study will inform owner agencies of the range in GWP that they may expect when provided with a single GWP value and of the changes in GWP that may occur if one of these significant parameters (cement direct carbon intensity or transportation distance) changes.